Voltage-controlled digital oscillator VCDO1 by Tom Wiltshire ,visit Electric Druid homepage http://www.electricdruid.net/index.php for a full detailed PDF on this Oscillator ,and more digital based synthesizer modules along with ASM code and assembled HEX code .
From the description on this Oscillator given there :

A single chip 1V/Oct voltage controlled digital oscillator, with 20 waveforms in a scannable wavetable.

The VCDO uses a PIC 16F1847 microprocessor to create a versatile and simple voltage-controlled 8-bit digital wavetable oscillator. All oscillator parameters are controlled by 0-5V control voltages. The chip has a native exponential control response, making interfacing with 1V/Oct control voltages very simple, even without an exponential convertor.